This invention relates generally to devices for the treatment of fractures in which soft tissue damage is present, and, more particularly, to a preassembled, unilateral external fixation device operable to reduce a bone fracture and to apply controlled distraction and compression at the fracture site of a bone.
A variety of activities such as high speed travel and the widespread use of heavy machinery in industry have in recent years increased the frequency of severely compounded and infected long bone fractures, such as the femur, tibia, radius and ulna, with accompanying damage to the surrounding soft tissue. In order to properly irrigate the wound and prevent infection of the soft tissue, it is necessary to avoid covering the affected area except with appropriate dressings. Casts may not be used for the treatment of long bone fractures where soft tissue damage is present.
The earliest method of treatment of these cases, which is still used today, involves placing the patient in traction to completely immobilize the affected limb. As is well known, there are many problems attendant to long term confinement of a patient to a bed including necrosis and muscle atrophy. In order to limit the use of traction in the treatment of fractured bones with attendant soft tissue damage, research begun in the 1930's resulted in the development of external skeletal fixation devices. These devices generally comprise a set of retaining pins secured to the bone on each side of the fracture which are adjustably connected to a frame.
An external fixation device commonly used today is the so-called Hoffmann system originally developed in the late 1930's. The Hoffmann fixation system includes two sets of self-drilling and self-tapping transcortical pins each having a centrally located continuous thread. One set of two or three pins enters the soft tissue at one side of the fracture site, passes completely through the distal or proximal portion of the bone and then outwardly through the soft tissue on the opposite side. The same procedure is repeated for the other set of transcortical pins on the opposite side of the fracture. Each transcortical pin is connected at opposite ends to a frame which is adapted to permit translation and pivoting of the pins for properly aligning the distal and proximal bone portions. The frame is adjusted during the surgical procedure to properly align the bone portions, and controlled distraction or compression may be applied post-operatively to maintain the fractured bone portions in engagement and in alignment.
Known external fixation devices incorporate different frame configurations for supporting the transcortical pins such as bilateral, triangular, circular and quadrilateral frames. The above-described Hoffmann device employs a quadrilateral frame. In each of these prior art fixation devices, transcortical pins are used to support the fractured bone portions, which, as described above, extend completely through the soft tissue and bone in the affected limb.
Several problems are encountered with the use of transcortical pins, and with the various frame designs for properly positioning the pins in the distal or proximal bone portions. Assume a patient has a femoral fracture with substantial soft tissue damage at one or more locations along the thigh. The transcortical pins are first inserted into the soft tissue on the distal and proximal side of the fracture. The surgeon can manipulate each transcortical pin around nerves and arteries in the soft tissue until it contacts the femur and begins to enter the cortical bone. At that point, the path of the pin is fixed and no further manipulation is possible. There is a substantial risk of nerve and arterial damage as the pin passes through the femur and then through the soft tissue in a fixed path on the opposite side of the leg. Each of the quadrilateral, circular, triangular and bilateral external fixation devices utilizes transcortical pins.
A second major problem with existing external fixation devices, and particularly the Hoffmann device, is that the frame elements for supporting the transcortical pins are not preassembled but must be assembled by the surgeon during the operation. An assortment of clamping elements and adjustment mechanisms forming the Hoffmann frame are provided to the surgeon in separate pieces and must be fitted together and then clamped to the transcortical pins during the surgical procedure. It has been found that unless the surgeon has great familiarity with the Hoffmann device, or other unassembled frame devices, there may be a reluctance to employ an external fixation device at all.
Another disadvantage of known external fixation devices is the difficulty in adjusting the position of and force exerted by the retaining pins, both during and after an operation. During a surgical procedure and post-operatively, external fixation devices must be capable of adjustment to vary the position of the bone portions and to control distraction and compression at the fracture side. It is often desirable to make relatively minor corrections of the position or force exerted by a set of retaining pins on one side of the fracture. However, in the Hoffmann quadrilateral fixation device, movement of the frame elements to adjust the position of one set of retaining pins in any direction requires adjustment of other frame elements associated with the other set of retaining pins. This feature of the Hoffmann device unduly complicates post-operative adjustment procedures which further reduces the willingness of physicians to employ such devices.
As stated above, one purpose of external fixation devices is to enable patients to move about and reduce the incidents of necrosis and other problems caused by confinement to bed. Many of the frame designs for securing transcortical pins, including the Hoffmann quadrilateral system and circular frames such as shown in U.S. Pats. Nos. 4,365,624 and 4,308,863, are extremely bulky and make it difficult for the patient to walk or otherwise move about. In addition, bulky frames often cover the fracture site and obstruct X-rays. While the retaining pins must be firmly secured to apply the necessary force to the fractured bone portions, it is desirable to make the frame as light as possible without obstructing the fracture site.